The volcanic rock from the Niangniangshan Formation in the Ningwu (Nanjing—Wuhu) volcanic basin is used for Rb-Sr isotopic dating. The Rb and Sr isotopic ratios of whole rock, Kfeldspar, plagioclase and biotite form a good linearity in n(87Rb）/n(86Sr） vs. n(87Sr）/n(86Sr） space. The isochron age of innerminerals is 1331±32 Ma (MSWD=0096), which represents the formation age of the volcanic rocks from the Niangniangshan formation. This age is consistent in error with that of underlying volcanic rocks of the Longwangshan and the Dawangshan formations. Chronological comparisons indicate that the volcanic rocks from the Luzong (Lujiang—Zongyang) and Ningwu volcanic basins were formed during a shortterm around 130 Ma, implying that the extension of the Lower Yangtze region might achieve its maximum at ca 130 Ma.